Phd in EARTH SCIENCES

Thesis title: Investigation of mineral inclusions trapped in lithospheric diamonds with implications for their origin and ascent rate

Diamonds provide a unique window into the inaccessible region of the Earth’s mantle, preserving unique information about its mineralogical, chemical composition, oxidation state, and volatile budget. Through the study of mineral and fluid inclusions, diamonds offer critical insights into the carbon, nitrogen, and hydrogen cycles, as well as the physicochemical processes that operate under these pressure-temperature conditions. Diamond inclusions have validated hypotheses previously proposed by geophysical models, high-pressure experiments, and meteoritic analogues, bnringing ground validated truth to mantle models. Beyond inclusions, the investigation of diamond lattice defects, morphology, and microstructures reveals valuable information on residence times, thermal histories, and ascent mechanisms. In particular, diamonds can provide direct evidence of metasomatic events and carbon rich fluids and rock interactions in the lithospheric mantle, recording dynamic processes that govern volatile transport and redox evolution at depth. This thesis addresses the challenges of interpreting diamond-based records by integrating spectroscopic, geochemical, and thermodynamic approaches to reconstruct the evolution of both diamonds and their inclusions. The research combines nitrogen thermochronometry with elastic geobarometry, oxybarometry, and high-resolution spectroscopic and chemical analyses to define realistic pressure–temperature–fO2 pathways for lithospheric diamonds. These results clarify how metasomatic reactions, redox variations, and ascent kinetics influence both the chemical composition and mineralogical phase inclusions and the defects information preserved in their host diamonds. The thesis is structured into five studies, two of which have been already published in peer reviewed journals such as Frontiers in Geochemistry and Diamond and Related Materials. Combined, these works explore: (1) the interaction of silicate inclusions with carbonated melts in lithospheric diamonds from the Juína region (Brazil); (2) the spatial distribution of nitrogen and hydrogen in peridotitic diamonds from the Siberian craton; (3) microdomain heterogeneities of N-H-related defects and their interactions with inclusions belonging to eclogitic diamonds; (4) the mineralogical changes of garnet in carbonate-rich fluids under analogue fibrous diamond-forming conditions; (5) The redox heterogeneties present in the lithospheric mantle of the Siberian Craton. Together, these studies refine our understanding of the redox state, mineralogical heterogeneity, and volatiles budget of the lithospheric mantle. They demonstrate that diamonds are not static records but dynamic archives that integrate deep-Earth processes across multiple scales.